enum NotificationType {
  chat, // 即时通讯消息
  app, // 应用内通知
  system, // 系统通知
  promotional, // 推广通知
}

class NotificationModel {
  final String title;
  final String body;
  final NotificationType type;
  final DateTime timestamp;
  final String? payload;

  NotificationModel({
    required this.title,
    required this.body,
    required this.type,
    required this.timestamp,
    this.payload,
  });
}
